The fruity odour note typical of black-currant is particularly well appreciated in modern perfumery. Up to now however it could not be easily reproduced by making use of prior known ingredients, black-currant buds absolute e.g. : this expensive fragrant material of natural origin possesses in fact a rather complex odour wherein the typical fruity note is often associated with undesired tonalities. In the same context, one can cite synthetic compounds such as 2,6,9,10,10-pentamethyl-1-oxa-spiro[4.5]deca-3,6diene and 2,6,9,10-tetramethyl-1-oxa-spiro[4.5]deca-3,6-diene, of formulae ##STR3## respectively, known in the art as possessing a fresh, green and natural odour reminiscent of that of mint leaves, clary sage and black-currant, as well as a fruity flavour more or less reminiscent of that of citrus fruits, grape-fruit more particularly (see DE-OS 2,634,077 and DE-OS 2,749,511, respectively).
Menthone-thiol-8 of formula ##STR4## also develops a fruity odour of black-currant type which odour is however associated with a sulfury tonality (see DE-PS 2,008,254). Menthone-thiol-8moreover is of limited interest in perfumery in view of its lack of stability in soaps, shampoos and detergents.
Contrary to the teaching of the art, the compound of formula (I), viz. 6-ethyl-2,10,10-trimethyl-1-oxa-spiro[4.5]deca-3,6-diene possesses a "clean" fruity note of black-currant type, namely free from any sulfury tonality. In view of its stability in soaps, detergents or house-hould materials, it can be moreover more widely used in perfumery than the prior known analogous odoriferous ingredients.
In the field of perfumery, compound (I) is characterized by an original odour note of black-currant type, free from sulfury tonality, reminiscent of the fruity note of black-currant buds absolute. It can be added to a great number of perfume compositions of different types such as fruity, fresh, minty, flowery, rosy, woody or chypre compositions e.g., wherein it efficiently develops its typical black-currant note.
In order to achieve such an original olfactive effect, compound (I) can advantegously be used as unique fragrant ingredient, for example in the form of solution in conventional solvents such as ethyl alcohol, diethyl phthalate, dipropylene-glycol or ethyl citrate e.g., or in admixture with the perfuming ingredients commonly used in the art, in that case in the form of a perfume base e.g. Compound (I) is appreciated in fine perfumery as well as in the preparation of perfumed products such as soaps, detergents, shampoos, cosmetics or house-hold materials, e.g.
The olfactive effects which can be achieved by making use of compound (I) greatly depend on the concentration, the nature of the fragrant coingredients or the nature of the material to which it is added. For the preparation of perfume compositions e.g., interesting effects can be achieved by using proportions as low as 0.05% of the weight of the composition. Characteristic olfactive effects are generally obtained by using compound (I) in proportions comprised between about 0.1 and 5%. Higher proportions, 20% or even more of the weight of the perfume composition can also be used, especially when particular odoriferous effects are desired.
In the field of flavours, compound (I) is characterized by its typical fruity and woody taste, reminiscent of that of black-currant. The said compound can thus be used for preparing artificial fruity flavours such as black-currant, raspberry or other red berries flavours, wherein it advantageously developes a fresh, fruity and woody flavour note, reinforcing at the same time the natural aspect of such flavour compositions.
Compound (I) can also be used for flavouring foodstuffs, beverages, pharmaceutical preparations or tobacco products. Flavouring effects such as those described hereinabove can be achieved by using the said compound in proportions comprised between about 0.01 and 10 ppm (parts per million), preferably between about 0.1 and 5 ppm of the weight of the thus flavoured material. Proportions superior to 10 ppm can also be considered, especially when particular flavouring effects are desired.
According to the process of the invention (method A) 2-ethyl-6,6-dimethyl-cyclohexanone can be first reacted with but-1-yn-3-ol, in the presence of a strong base. Suitable strong bases are mineral organic bases such as potassium hydroxide, butyl-lithium, potassium tert-butoxide or sodium or lithium amide e.g. Although this does not represent a necessary condition for achieving high yields of final product, the said reaction can be effected in the presence of inert organic solvents: in this case ethers, aliphatic or aromatic hydrocarbons or mixtures of same are preferred. The said reaction is moreover carried out at a temperature generally comprised between about 25.degree. and 55.degree. C., preferably of the order of 33.degree. C.
After subsequent hydrolysis there is isolated a novel intermediate compound having the formula ##STR5## which is subsequently subjected to acidic treatment. The said acidic treatment is effected by means of a strong mineral or organic acid, preferably in an aqueous organic medium. Suitable organic solvents are those defined in the preceeding reaction step; suitable strong acids are formic, phosphoric, sulfuric, polyphosphoric, benzenesulfonic or p-toluenesulfonic acids e.g. or even an acidic diatomaceous earth. The said acidic treatment is preferably effected at a temperature comprised between about 50.degree. and 100.degree. C., more generally at the boiling temperature of the reaction mixture.
According to another embodiment of the process of the invention (method A) compound (I) can also be obtained from 2-ethyl-6,6-dimethylcyclohexanone, by reacting the same with an organo-metallic derivative of formula ##STR6## as previously defined, hydrolysis and subsequent acidic treatment of the hydrolization product. In this case, the same reaction conditions as those applied hereinabove can advantageously be used.
According to a further embodiment of the process of the invention (method B),2ethyl-6,6-dimethyl-cyclohex-2-en-1-one can be reacted with an organo-metallic derivative of formula (II) as defined hereinabove, in the conditions of a Grignard reaction. After subsequent hydrolysis there is isolated a novel intermediate compound having the formula. ##STR7## wherein R is different from Mg-halogen. The said intermediate compound is then subjected to hydrogenation, in the presence of a metal catalyst such as Raney nickel or in the presence of a partially inactivated catalyst, Lindlar catalyst e.g. There is thus obtained a further novel intermediate compound of formula ##STR8## wherein R is different from Mg-halogen, which is finally subjected to an acidic treatment to afford compound (I). The said acidic treatment can be effected in the same conditions as those applied for the compound of formula (III).
As obtained from the above described syntheses, compound (I) may exist in the form of a mixture of stereoisomers A and B (see hereinafter) ##STR9## or in the form of one of the above stereoisomers. Formula (I) as defined in the invention is deemed to represent either single stereoisomers or mixtures of same. For practical and economical reasons however, compound (I) is used in accordance with the invention as directly obtained from the described process.